Spaceprobes in the Solar System

The diagram above (click to zoom) and list below show currently active spacecraft in the Solar System, not including those operating close to the Earth (and I’ve probably missed a few):

  • Voyager 1 and Voyager 2, launched in 1977, now heading into the darkness and still reporting back, even though they are over 17 billion km or 16 light-hours away (not shown above).
  • Cassini–Huygens, launched in 1997, now in the final stages of its exploration of Saturn (see fact sheet).
  • 2001 Mars Odyssey, launched in 2001, and still orbiting Mars.
  • New Horizons, launched in 2006, now en route from Pluto to the Kuiper belt object 2014 MU69, which it should reach in January 2019.
  • Dawn, launched in 2007, currently orbiting Ceres (image shown above the Earth).
  • Akatsuki, launched in 2010, currently orbiting Venus, which it will do until 2018.
  • Juno, launched in 2011, currently orbiting Jupiter, which it will do until February 2018.
  • Hayabusa 2, launched in 2014, currently en route to asteroid 162173 Ryugu, which it should reach in 2018. It will then take a sample which should arrive back home in 2020 (not shown above).
  • ExoMars Trace Gas Orbiter, launched in 2016, currently orbiting Mars and mapping the Martian atmosphere (the associated Mars lander was lost in 2016).
  • OSIRIS-REx, launched in 2016, currently en route to asteroid 101955 Bennu, which it should reach in 2018. It will then take a sample which should arrive back home in 2023 (image shown below the Earth).

In addition to the above, BepiColombo is scheduled to launch for Mercury in October 2018, and SolO is scheduled to launch for the Sun that same month. Also, InSight is scheduled to launch for Mars in May 2018, and Solar Probe Plus is scheduled to launch for the Sun in August 2018.


Metallic hydrogen

It has long been known that hydrogen forms a metallic solid at moderate to low temperatures and extremely high pressures. Last year, Ranga Dias and Isaac F. Silvera at Harvard University were the first to actually produce this metal, using the enormous pressure of 495 gigapascals (see their paper).

At higher temperatures, hydrogen forms a metallic liquid, and this is believed to exist at the heart of Jupiter and Saturn. This liquid has yet to be observed.

Looking back: 2000

As the year 2000 opened, I was in Sydney, watching the New Year’s Eve fireworks. After all the hype about the Y2K problem, I was half-expecting the lights to go out. They did not, of course. Later in the year, the 2000 Summer Olympics were held in Sydney, and the city put on another spectacular show for that:

Also in 2000, genome-sequencing of the plant Arabidopsis thaliana (below) was completed, and described in Nature. The genome is available at

The Cassini probe flew past Jupiter at the end of the year (en route to Saturn), and took some spectacular pictures, including this one of Io in front of the planet:

Films of 2000 included Chicken Run, Chocolat, Gladiator, Pitch Black, Proof of Life, The 6th Day, Thirteen Days, X-Men, and the excellent O Brother, Where Art Thou?.

In books, Ross King published a wonderful little book about Brunelleschi, Dan Brown published the wildly inaccurate Angels & Demons, Umberto Eco published Baudolino (in Italian), J.K. Rowling published the 4th Harry Potter book, and Patricia McKillip published the beautifully oneiric The Tower at Stony Wood.

In music, Britney Spears was still wildly popular. In architecture, the Cathedral of Christ the Saviour in Moscow was rebuilt, and the Tate Modern in London opened. The London Millennium Bridge was closed two days after opening because of resonance problems, which required the retrofitting of fluid-viscous and tuned-mass dampers. Software is not the only thing with bugs.

Juno arrives!

The Juno spaceprobe (above) is just an hour away from orbit insertion around Jupiter. Juno has been in transit, waiting for this day, for almost five years. Juno is solar-powered, with huge 9-metre-long solar panels, to compensate for the fact that the intensity of sunlight around Jupiter is only 4% of what it is here.

Follow the spaceprobe on Twitter or watch the live NASA feed (which is starting now).

Update 1: Juno is into its orbit insertion burn, screaming past Jupiter at a distance of 5,000 km and a velocity of 208,000 km/hr.
Update 2: Engine off. “Juno, welcome to Jupiter!” (NASA/JPL clapping)

Arriving at Jupiter

The Juno spaceprobe (above) is a few days from reaching Jupiter, and beginning its mission of studying that giant planet. Juno has been in transit for almost five years, as shown below:

Juno is now just under 4 million kilometres away from Jupiter. She will spend more than a year examining Jupiter in detail, and will then deorbit, carrying a plaque in honour of Galileo, who discovered that there were moons orbiting that planet.

As seems to be the norm nowadays, the spaceprobe has a Twitter feed for staying in touch. There will certainly be some interesting stories and pictures to come!

Venus and Jupiter in conjunction

The planets Venus and Jupiter were in conjunction last night, as the photograph above (by Neal Simpson) shows. The diagram below (by the Fourmilab) shows why: although Venus is much closer to Earth (and thus much brighter), the three planets are almost in a straight line. Venus and Jupiter should still be pretty close in the sky for the next few nights.